media: ngene: BUG: spinlock bad magic in irq_handler() on early IRQ

[Jaeyoung Chung]

Hi,

ngene_start() in drivers/media/pci/ngene/ngene-core.c registers the
interrupt handler with request_irq() before it initializes
dev->cmd_lock with spin_lock_init(). If an interrupt arrives before
spin_lock_init() runs, the handler acquires an uninitialized spinlock,
which triggers a kernel warning.

The probe path, in ngene_start():

    stat = request_irq(dev->pci_dev->irq, irq_handler,
                       IRQF_SHARED, "nGene", (void *)dev); /* register handler */
    ...
    spin_lock_init(&dev->cmd_lock);                        /* initialize lock */

The interrupt handler, irq_handler(), takes the lock:

    spin_lock(&dev->cmd_lock);

If the device raises an interrupt before spin_lock_init() runs, the
handler acquires dev->cmd_lock while it is still uninitialized, which
triggers "BUG: spinlock bad magic" when CONFIG_DEBUG_SPINLOCK is
enabled.

Suggested fix: move spin_lock_init(&dev->cmd_lock) above request_irq(),
so the lock is valid before the handler can run.

Reported-by: Sangyun Kim <sangyun.kim@xxxxxxxxx>
Reported-by: Kyungwook Boo <bookyungwook@xxxxxxxxx>

Thanks,
Jaeyoung Chung